Modern scientific and technological move towards concrete production is aimed at achieving sustainable and affordable concrete construction. This move has led to the search for non-conventional local supplementary cementitious materials (SCM’s) including the possibility of using industrial and agricultural based pulverized and combustible wastes in concrete construction. In this study, an experimental investigation was conducted on the potential use of sheanut shells ash, derived from the combustion of sheanut shells – an agro-based waste, as partial replacement of cement in concrete. The cement content in the concrete mix was partially replaced 0%, 10% and 20% by mass with sheanut shells ash. The effect of the ash on setting time and workability were examined. Five concrete cubes were prepared for each of the replacement levels from which three cubes were randomly selected from each replacement level and tested for compressive strength at three stages of curing age (14, 28 and 90 days). There were high and minimal reductions in the compressive strengths of the experimental cubes over the control cubes at the 14 and 28 curing age respectively. However, there was a significant increase in strength of the experimental cubes over the control cubes at the 90 days curing age. Though the ash has an improved increasing effect on strength, the findings will limit it use in situations where long term strength development is required.

1. Research Inventy: International Journal of Engineering And Science
Vol.6, Issue 6 (July 2016), PP -21-27
Issn (e): 2278-4721, Issn (p):2319-6483, www.researchinventy.com
21
Experimental Investigation of Sheanut Shells Ash as Partial
Replacement of Cement for Sustainable and Affordable
Concrete Production
Zievie, P1
, Yalley, P. P2
, Saan, R.3
1,3
Department of Building Technology and Estate Management, School of Applied Science and Technology, Wa
Polytechnic, Wa, Ghana,
2
Department of Construction Technology Education, College of Technology Education, University of Education,
Winneba, Ghana,
Abstract: Modern scientific and technological move towards concrete production is aimed at achieving
sustainable and affordable concrete construction. This move has led to the search for non-conventional local
supplementary cementitious materials (SCM’s) including the possibility of using industrial and agricultural
based pulverized and combustible wastes in concrete construction. In this study, an experimental investigation
was conducted on the potential use of sheanut shells ash, derived from the combustion of sheanut shells – an
agro-based waste, as partial replacement of cement in concrete. The cement content in the concrete mix was
partially replaced 0%, 10% and 20% by mass with sheanut shells ash. The effect of the ash on setting time and
workability were examined. Five concrete cubes were prepared for each of the replacement levels from which
three cubes were randomly selected from each replacement level and tested for compressive strength at three
stages of curing age (14, 28 and 90 days). There were high and minimal reductions in the compressive strengths
of the experimental cubes over the control cubes at the 14 and 28 curing age respectively. However, there was a
significant increase in strength of the experimental cubes over the control cubes at the 90 days curing age.
Though the ash has an improved increasing effect on strength, the findings will limit it use in situations where
long term strength development is required.
Keywords: Sheanut shells ash, partial replacement, setting time, workability, compressive strength
I. Introduction
According to Abraham Maslow theory of motivation, one of the physiological needs of human beings
is shelter. But any time the issue of shelter or housing is tabled for discussions by policy makers, terms like
“housing deficit” and “housing inadequacy” dominate, but we actually live in a “housing desperate” world.
Research findings indicate that people who live in developed countries are “housing rich” but those living in
developing countries are “housing poor” and infact, “housing desperate” [1]. The global and national statistics
are horrifying. In the global picture, it had been reported that more than 1000 million people throughout the
world live in grossly inadequate housing while more than 100 million people have no housing whatsoever [2].
In the national front, it has been found that Ghana’s housing deficit stands at an estimated number of 1.7 million
units and is expected to double by the year 2025 if steps are not taken to address the situation [3].
The over dependence on conventional concrete materials, especially cement, which raw materials are
mostly imported, in concrete and mortars for housing in developing countries is largely responsible for the
continuous increase in housing cost. The importation of clinker and gypsum alone for the production of Portland
cement, used extensively in Ghana, costs the nation not less than 180 million US Dollars annually [4].
Therefore, it is advisable for developing countries to take cost and content of cement in concrete into
consideration and develop new technologies that would employ the use of local based supplementary
cementitious materials (SCM’s) through research to facilitate the provision of sustainable and affordable
concrete construction [4].
These supplementary cementitious materials according to Thomas (2002) include all pozzolans and
hydraulic materials that contribute to the properties of concrete through pozzolanic or hydraulic activity, or both
when used in conjunction with cement [5]. Pozzolans are defined as siliceous and aluminous material which do
not possess cementitious property in itself, but reacts in the presence of water with the lime at the normal
temperatures to form compounds of low solubility having cementitious properties [6]. Pozzolanic supplementary
cementitious materials that are commonly used in concrete production are fly ash, silica fume, calcined clay and
volcanic ash, while those SCM’s that are hydraulic in behavior are ground granulated blast furnace slag and fly
ash with high calcium contents [5].
In the olden days, the use of SCM’s as partial replacement of cement in concrete production to save
cost and modify some properties to suit specific requirements in some ancient civilized countries had been

2. Experimental Investigation of Sheanut Shells Ash as Partial Replacement of Cement for Sustainable…
22
reported. Historical reports indicate that the Romans added volcanic ash to concrete to save cost and also
allowed it to set under water while the Egyptians added horse hair and animal blood to concrete to make it less
liable to crack while it hardened and also to make it more frost resistant [7]. The potential use of fly ash in
concrete has been known almost since the start of the 19th
century [8], although it was not until the mid 1900s
that significant utilization of fly ash in concrete began following the pioneering research conducted at the
University of California, Berkeley [9].
Presently, the use of SCM’s in concrete production is geared towards the utilization of local based
industrial and agricultural by-products in the interest of providing sustainable and affordable concrete
construction to satisfy the housing needs of majority of the poor in developing countries [10], [11], [12] and
[13]. The concept of sustainable and affordable concrete construction was introduced in the UK where the
government sponsored many research projects concerning environmental issues, reduction in waste, use of
industrial and agricultural by-products, as well as recycling products of demolition. Sustainable and affordable
concrete construction is the prudent use of natural materials as constituents of concrete, so that they remain
available for future generations and be affordable to meet their housing needs. The increased in the awareness of
this principle has led to more research work aimed at optimum and prudent use of cement and its total or partial
replacement with by-products such as fly ash, blast furnace slag, etc [14]. It is in pursuance of this principle that
an attempt is made in this paper to investigate the pozzolanic reactive effect of sheanut shells ash (SSA) as
partial replacement of cement on concrete setting time, workability and compressive strength.
Sheanut shells ash (SSA) is an agro-based by-product derived from the combustion of sheanut shells as
a way of waste disposal during the processing of shea butter which is one of the most commonly used food
hydrocolloids in Ghana. The butter has many uses and applications; the matured fruit is edible and as such eaten
as a fruit; when refined, the oil is used for cooking, frying and even as a substitute for the more valuable dairy
butter. Due to its exceptional healing qualities, it is used globally as a body lotion, scalp and hair applications;
for high quality cosmetics and quite recently, in the aromatherapy industry [15]. The commercial use of the
shells and the shells ash has not been explored except that the ash is soaked and the soaked water squeezed out,
and used locally in making soap for washing and bathing purposes. The shea tree grows mainly in tropical
savannah regions of Africa and South America. Ghana produces about 200,000 tonnes of sheanuts annually and
according to [16] is the leading producer in the world followed by Burkina Fasso, Ivory Coast, Togo, Mali,
Benin and Nigeria in that order. Hence, the availability and affordability of the burnt shells ash in the study area
is guaranteed.
II. Materials and Methods
2.1 Materials Used
Sheanut shells ash (SSA) was used in this study as a supplementary cementitious material to partially
replace the cement content in the concrete. The ash was obtained from a local shea butter extraction waste
dumping/burning site at Fielmuo near Nandom in the Upper West Region of Ghana. Good quality natural river
sand and stones of up to 30mm nominal maximum size, sourced from a local construction site were used. Tap
water with the quality conforming to BS 3148: 1980, available in the laboratory supplied by the Ghana Water
Company Limited (GWCL) was used for all mixes [17]. Finally, “Ghacem”, a commercial ordinary Portland
cement brand produced in Ghana in conformity with BS 4027: 1986 specifications for Portland cement was used
[18].
2.1.1 Sheanut Shells Ash Chemical Analysis
The sheanut shells, for the purpose of this study refer to the outer hard covering of the nut (Fig 1). The
shells were subjected to control burning in the open air amidst constant turning up with a long metallic rod with
wooden handle, to ensure even combustion so as to improve the ash pozzolanic properties as recommended
[19]. The ash was left to cool and was sieved through a 325 mesh 45μm sieve to eliminate any un-burnt and
other unwanted matter from the fine powdered ash (Fig 2). The fine ash was parceled and sent to the Agro-
Forestry Department Laboratory of the Kwame Nkrumah University of Science and Technology, Kumasi, where
the chemical analysis was done using different methods as a guide with focus on pozzolanic and hydraulic
reactive properties.
Figure 1: Sheanut Shells Figure 2: Sieved Sheanut Shells Ash (SSA)

3. Experimental Investigation of Sheanut Shells Ash as Partial Replacement of Cement for Sustainable…
23
2.1.2 Aggregates Characteristics
The aggregates quality and suitability properties were investigated at the Wa Polytechnic Building
Technology laboratory. The sampling and testing were carried out in accordance with requirements of the
appropriate parts of the BS 882: 1992 [20]. The following characteristics were studied; specific gravity, water
absorption, fineness modulus, abrasion, flakiness index and elongation index.
2.2 Setting Time
Cementing materials in concrete mixes are expected to retain their plasticity for at least 30 minutes
from the time water is mixed to it [21]. The impact of ashes including fly ash on the setting behavior of concrete
has been studied. It has been found that high calcium ashes generally retard setting to a lesser degree than low
calcium ashes, probably because the hydraulic reactivity of ash increases with increasing calcium content [5].
Therefore, the test is meant to study the effect of the ash used on the setting behavior of the concrete.
The cement content in the test specimens was replaced 0%, 10% and 20% by mass with an equal mass
of sheanut shells ash (SSA) and labeled as A0 (control specimen), B10 and B20 (experimental specimen). The
water content needed to prepare the cement and SSA content test blocks to obtain the desired consistency for the
setting time test was determined through the standard consistency test using the Vicat apparatus in conformity
with BS 4550 – 3.5 specifications for the determination of standard consistency [22]. The test blocks were made
with the appropriate cement/SSA/contents and the required amount of water for each replacement level. The
blocks were then tested for the initial and final setting times using the initial set and final set needles
respectively in the Vicat apparatus in accordance with BS 4550 – 3.6 specifications for setting time test [22].
2.3 Workability Measurement
The effect of carbon contents in fly ash and other ashes on fresh concrete workability has been
investigated. Research findings indicate that finer and low carbon content ash reduces the water demand of
concrete while coarser and high carbon content ash increases the water demand. It is therefore recommended
that each 10% of ash content should allow for a water reduction or increase of at least 3% depending on the
fineness or coarseness and carbon content [5].
The slump testing method was used because of its simplicity and suitability for concrete mixes of
medium to high workabilities (25 – 125mm slump) using stones of up to 30mm nominal maximum size. The
preparation of the mix for the slump test was performed in accordance with BS 1881 – 125: 1986 specifications
for fresh concrete in the laboratory [23]. The required quantities of the materials for the mix were batched by
weight. Trial tests were conducted on concrete mixes with varied water contents in order to obtain an optimum
water content to produce the normal mix (A0) with a true slump. A water/cement ratio of 0.5 recorded a true
slump and was used for the normal mix (A0). The SSA is coarser and has a high carbon content of 4.25 (Table
4), hence a 5% increase of water content was allowed for at each replacement level. Therefore, a
water/cement/SSA ratio of 0.53 and 0.56 were used for the experimental mixes B10 and B20 respectively. The
mixing was done by hand in a clean head pan. The cement, sheanut shells ash (SSA) and sand were first mixed
in a dry state until they were thoroughly blended before the stones were added and the entire mixes turned
severally until the stones were uniformly distributed in the mix. Water was then added in two phases while the
mixing continued until a uniformed colour and desired consistency was achieved. The slumps for all the mixes
were measured using the slump cone.
2.4 Compressive Strength
The effect of partially replacing a certain mass of cement with an equal mass of low calcium fly ash has
been established. Studies found that as the level of replacement increases the early age strength decreases. Long
term strength development is improved when ash is used and at some age the strength of the fly ash concrete
will equal that of the cement concrete so long as sufficient curing is provided. Sufficient moulds measuring 150
x 150 x 150mm were available in the laboratory to enable all the cubes to be cast from the same mix in the same
day. This was aimed at eliminating discrepancies such as variations in temperature, water content, mix
proportion and compaction, which might have arisen if more than one day was used to cast the cubes. The cubes
were removed from the moulds the next day and marked A0, B10 and B20 for the 0%, 10% and 20% cement/SSA
contents replacements levels respectively and submerged in water for curing. Three cubes from each
replacement levels were randomly selected from the curing water after 14, 28 and 90 days of submission and
tested for the 14, 28 and 90 days compressive strength using the compression testing machine (Fig 3).

4. Experimental Investigation of Sheanut Shells Ash as Partial Replacement of Cement for Sustainable…
24
Figure 3: Concrete cube being crushed
III. Results and Discussions
3.1 Sheanut Shells Ash Chemical Compounds and Contents
The calcium, silica, aluminium, and carbon contents have been found to be the best indicators of how
the ash will behave in concrete, although other compounds such as iron, sulphate, magnesia and many others
can also affect the ash performance. The calcium content is useful in predicting how effective the ash will be in
terms of reducing the heat of hydration [24], controlling expansion due to alkali-silica reaction [25], and
providing resistance to sulphate attack [26]. Suitable percentage ranges and limits for compounds in ash for
concrete production have been established. Previous studies recommended the following ranges; calcium 1 –
8%, silica 30 – 60%, aluminium 15 – 30%, carbon 1 – 30% [6]. It has also been reported that low calcium fly
ash (< 8%) are pozzolanic and display no significant hydraulic behavior [5], the ASTM C618 specifications for
fly ash indicated that in addition to having pozzolanic properties the ash also has some cementitious properties if
the sum total of the percentages of the oxides (silica, aluminium and iron) is equals to or greater than 50% [27].
In Table 1, the results of the chemical analysis of the sheanut shells ash (SSA) are presented. It could be noticed
that the calcium content is 1.81%, far less than the 8% limit. Again, the total sum of the oxides (Si02 + Al203 +
Fe203) is 50.19%, slightly exceeding the 50% minimum limit. Thus, the SSA used in the study has both
pozzolanic and cementitious properties and may display no significant hydraulic behavior.
Table 1: Chemical Properties of SSA
Compounds Symbol Results (%) Test Method
Calcium Ca0 1.81 EDTA Titration
Silica Si02 29.01 Gravimetric
Aluminium Al203 20.05 spectrophometric
Carbon LOI 4.25 Gravimetric loss of weight on ignition
Iron Fe203 1.13 Spectrophometric
Magnesia Mg0 1.48 EDTA Titration
Sodium Na20 0.26 Flame photometric
Potassium K20 1.7 Flame photometric
Phosphorus P203 0.29 Spectrophometric
3.2 Aggregates Characteristics
The characteristics of the natural river sand and stones used in this investigation, determined using the
British Standards are presented in Table 2.
Table 2: Characteristics of the Aggregates used
Test conducted Stones Sand
Results BS Limits Results BS Limits
Bulk specific gravity 2.60 2.6 – 2.75 2.61 2.6 – 2.75
Apparent specific gravity 2.68 2.6 – 2.75 ----- ------
Water absorption 1.96% 20% max 11.6% 20% max
Fineness modulus 7.0 5.5 – 8.0 3.26 2.0 – 3.5
Abrasion strength 25.6% 40% max ------ -------
Flakiness index 12% 15% max ------ -------
Elongation index 9% 10% max ------ -------
3.3 Setting Time
Fig 4 presents the results of the setting time test conducted. There is a steady increase of setting time
from A0 to B20 for the initial and final setting times. The calcium content present in the SSA is low and as such
this outcome is expected because hydraulic reactivity in ash decreases with decreasing calcium content.

5. Experimental Investigation of Sheanut Shells Ash as Partial Replacement of Cement for Sustainable…
25
Figure 4: Setting behavior of SSA content in fresh concrete mix
3.4 Slump Test
The slump test results are given in Table 3 and Fig 5. The values indicate a steady decrease of slump
from 115mm for A0 to 57mm for B20 even though the water content was increased by 5% at each replacement
level. This is an indicative that SSA is coarse with high carbon content, hence the higher the SSA in the mix, the
more the water content required to achieve a true slump.
Table 3: Slump Test Results
Mix W/C Ratio Slump (mm) Collapse height (mm) Degree of workability
A0 0.50 115 185 High
B10 0.53 82 218 High
B20 0.56 57 243 Medium
Figure 5: Slump behavior of SSA content in fresh concrete mix
3.5 Compressive Strength
The compressive strength test results are given in Table 4 and the effect of curing age on long term
strength development presented in Fig 6. Early age compressive strength is reduced as the SSA content
increases.
Table 4: Compressive Strength of Concrete Cubes (N/mm2
)
Cube 14 days 28 days 90 days
Values Mean Values Mean Values Mean
A0
18.71
18.58
19.02
18.77
23.16
22.13
22.53
22.61
26.76
27.29
26.13
26.73
B10
14.98
15.16
14.13
14.76
19.87
19.44
20.13
19.81
33.78
32.98
34.49
33.75
B20
9.82
10.80
10.49
10.37
17.42
16.93
17.96
17.44
30.31
29.33
30.36
30.00

6. Experimental Investigation of Sheanut Shells Ash as Partial Replacement of Cement for Sustainable…
26
Figure 6: Effect of curing age on compressive strength
A high reduction of strength of 21% and 45% was observed for the B10 and B20 respectively over the A0
at the 14 days curing age. The reduction in strength narrowed to a minimum of 12% and 23% for the B10 and
B20 respectively over A0 at the 28 days curing age. However, there was a significant increase of strength of 21%
and 11% for the B10 and B20 respectively over A0 at the 90 days curing age (Figure 6)
The mean compressive strength values for A0, B10 and B20 at each curing age (14, 28 and 90 days) were
compared using a One-Way Analysis of Variance (ANOVA) at a confidence interval of 95%. A high level of
variability between the individual cement/SSA content replacement levels existed in all the three curing ages
(Table 5). The ANOVA results therefore suggest that there is a statistically significant difference in the
compressive strength among the replacement levels in all the curing ages.
Table 5: Summary of ANOVA Results – Compressive Strength (N/mm2
)
Cubes curing and testing ages (days)
14 28 90
N 9 9 9
Missing 0 0 0
F – value 262.745 81.805 89.266
P – value 0.000 0.000 0.000
Significant at 0.05 (P – value)
IV. Conclusions
The findings from the chemical analysis suggest that SSA possesses both pozzolanic and cementitious
properties, with very little or no significant hydraulic properties since the sum total of the oxides is slightly
greater than 50% as specified in ASTM C618 – 05. More time is required for SSA content concrete cubes to set
because of it low calcium content. Therefore, other chemical additives could be added to reduce the setting time
in situations where speedy work is required. SSA is coarser in nature with high carbon content and therefore,
will require more water content at higher replacement levels to achieve a true slump. The short term
compressive strengths of cement/SSA content concrete cubes were reduced whiles the long term strength was
higher than normal concrete at the 90 days curing age.
It is therefore concluded that SSA is a potential supplementary cementitious material (SCM) for
concrete construction in a bid to save the cost of materials in concrete production. Sheanut shells ash (SSA) can
be used in situations where long term strength is required. The wide search for cheap and local alternative
industrial and agricultural based waste materials as supplementary cementitious material for sustainable and
affordable concrete construction will enhance and promote the adoption and use of SSA as partial replacement
of cement in concrete.
Acknowledgement
The effort of Kele Chrysantus, a past student of the Department of Building Technology and Estate
management, Wa Polytechnic, Wa, Ghana, is acknowledged for the preliminary role played in this experimental
research. The kind support and co-operation extended by Napoleon Mensah, a Lecturer in the Department of
Science Laboratory Technology, Wa Polytechnic, who sent the sheanut shells ash to the Agro-Forestry
Department Laboratory of KNUST, Kumasi for the chemical analysis to be done, and Technicians in the
Building Technology Department Laboratory of the Wa Polytechnic, who assisted in the compressive test of the
concrete cubes, in all the endeavors of the authors is recorded with deep sense of gratitude.

7. Experimental Investigation of Sheanut Shells Ash as Partial Replacement of Cement for Sustainable…
27
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